In the blocks around the bomb blasts, nothing about Tuesday was normal.

Back Bay office towers were eerily quiet and patrolled by armed guards. Workers had their bags checked at their buildings, or their cars at parking garages. And on streets usually bustling with people, the loudest noise came from the sky, as helicopters hovered above a district that remained on lockdown.

“It looks like Armageddon,” Connie DiCocco, said of Back Bay streets still covered in debris Tuesday. “Military everywhere and SWAT and weapons, FBI and media.”

Like many area companies, the Boylston Street offices of DiCocco’s nonprofit, the Alosa Foundation, remained closed as police searched for evidence related to the deadly Marathon bombings. In a large swath of the neighborhood, the frantic aftermath of the bombings seemed frozen in time: Water cups and silver capes blew in the breeze; tables at outdoor cafes were still set with plates of food that were abandoned when the bombs went off.

The offices at Marlo Marketing/Communications, located on the second and third floors of a Boylston Street building, sustained damage from the blasts, with windows unhinged from their frames and pictures blown off the walls.

“We just want to try to get back to normal as quickly as we can while recognizing that I don’t think anyone is going to feel normal in that neighborhood for quite some time,” said owner Marlo Fogelman. She doesn’t expect to get inside the office any time soon and asks clients to be patient as the firm tries to recover.

The company was hosting a Marathon party with around 100 people when the bombs exploded. All the guests fled out the back fire escapes while smoke billowed in through broken windows out front. Fogelman said investigators have already asked her and her guests to provide them with photos and video images taken before and after the explosions.

A few doors down, the Charlesmark Hotel remained closed, its lobby spattered with blood. Mark Hagopian, Charlesmark’s operating partner, said he was on the hotel’s patio when the first explosion occurred about 35 feet away. “It was like a cannon,” he said. “We knew something was wrong.”

Security was beefed up across the city Tuesday. Guards checked the bags in the lobby of State Street Corp.’s downtown headquarters, as well as cars entering the garage. Police also kept a close watch on South Station, where commuters had their bags searched throughout the day.

At the Hancock Tower, security staff in black suits stood alert in the lobby, while members of the National Guard manned the corner of St. James Avenue and Clarendon Street, behind the metal barricades still up from the Marathon.

A runner from Dublin stood looking at the shiny edifice in his blue-and-gold jacket. This was Sean Gillen’s first Boston Marathon; he finished in 3:58, early enough to have missed the blasts.

“It’s shocking no matter where this happens in the world,’’ he said.

On Newbury Street, a place typically bustling with fashionable shoppers, security guards and police in fluorescent yellow vests roamed around still-shuttered stores such as Cartier and Armani. A guard holding a submachine gun kept watch outside The Taj hotel.

Tom O’Brien, a regional manager for Joe’s American Bar and Grill, said the company posted a security guard at the door when it opened on Tuesday “to check people on the way into the restaurant and make it as safe as we can.”

O’Brien said Monday’s events could have a lasting impact on what is typically one of the Back Bay’s busiest and most festive times of the year. The company’s sister restaurants closer to the blasts, Abe & Louie’s and Atlantic Fish Co., remained shuttered on Tuesday. On a typical spring day, the three restaurants combined serve about 1,600 diners daily.

“We’re trying to give people in the neighborhood some place to gather and talk about what happened and have something to eat,” said O’Brien, whose chefs cooked 100 cheeseburgers during lunch for police and fire officials.

Many stores in the Prudential mall off Boylston Street were closed Tuesday morning, including Saks, Aldo, and l’Occitane. But Lorena Robles, who with her sister sells music accessories and knick-knacks from a Prudential mall kiosk called Got Music?, said they decided to remain open. “We need to keep working because what happened yesterday is really sad, but we have to show them we keep going,” Robles said.

At Forum, a bar and restaurant near where one of the bombs exploded, that is easier said than done. The eatery was hosting a large fund-raiser for the foundation of former New England Patriot Joe Andruzzi to benefit cancer patients. Euz Azevedo, owner of the firm that runs Forum, estimated that dozens of guests, staff, and spectators at the site were injured — several severely.

“The images of horror and pain that some of us witnessed will be hard to forget,” Azevedo wrote on the restaurant’s Facebook page, adding that Forum will be closed “until further notice.”